kerberized afpserver stopped working

Hello, I have had a nice working setup with a kerberized AFP server. However, since a few days now I get the tgt and the ticket for the afpserver/fileserver@DOMAIN.COM fine, but I cannot mount the volumes with the ticket. All I get is an error -5023. Since I have not found anything about debugging the kerberos communication on the server I don't know what to do. Mounting the volumes using password auth after destroying the tickets works fine. Any hints? Leo.